The present invention relates to a new and improved construction of synchronization apparatus for speed-changing gearing or transmissions --also sometimes referred to in the art as change-speed gearing--, particularly for vehicles or the like, comprising a slotted synchronization ring arranged between a claw or jaw support and a gear shift sleeve and a blocker body supported for radially outward movement at the claw support, and wherein the blocker body engages with play by means of an entrainment cam in the slot of the synchronization ring. Further, the synchronization ring during the synchronization function bears with one of its ends at the entrainment cam in the direction of the relative rotation which is to be compensated or equalized between the claw support and the gear shift sleeve.
Synchronization devices of this type basically operate in accordance with the principle of internal expanding jaw brakes. In fact the ring which is supported via one of its ends during the synchronization operation constitutes a brake jaw which bears from the inside against the gear shift sleeve corresponding to the brake drum. Stated in a more precise manner, the synchronization ring corresponds to a primary jaw or override jaw in that the friction related to the support brings about a radially outwardly effective moment and generally strives to open the synchronization ring, so that the same is pressed with a greater force against the gear shift sleeve than would be possible owing to its inherent elasticity.
According to the synchronization apparatus which has become known to the art from German patent publication No. 1,013,178 the servo action of the synchronization ring is increased in that the blocker body bears against impacts or stops of the claw support which are inclined with respect to the radial direction, and thus, is pressed by means of a work surface from the inside against the end which is free during the synchronization operation, i.e. against the abutting or so-called run-on end of the synchronization ring. Even the servo action which is increased without question with this arrangement is not sufficient to prevent a premature overtraveling or overriding of the synchronization ring.
Apparently in recognition of the aforementioned operation of this prior art synchronization apparatus there was developed a further state-of-the-art synchronization apparatus as taught in French Pat. No. 1,340,944 which likewise is based upon the principle of a friction brake and is constituted by a combination of an internal expanding brake and an external contracting band brake or outer band brake. With this prior art equipment during the synchronization operation a synchronization ring segment acting as an internal expanding brake jaw bears upon the end of a further synchronization ring functioning as a brake band or lining. Such prior art apparatus is complicated and possesses all of the therewith associated drawbacks. Also it does not provide any protection against a premature overriding of the synchronization.